1. Field of the Invention
The present invention relates in general to engine brake devices incorporated with an automotive internal combustion engine, and more particularly to decompression engine brake devices of a type which can exhibit higher engine braking effect irrespective of a simple construction thereof.
2. Background of the Invention
In automotive diesel engines, there is a type which has no throttle valve. For simplification of description, such type diesel engines will be referred to as "NTVDE" (viz., no throttle valve diesel engine). As is known, the throttle valve is an effective means for producing a negative pressure which produces a power for the engine braking. Thus, in motor vehicles powered by "NTVDE", there is such a tendency that the engine braking obtained by such vehicles is poor as compared with that obtained by motor vehicles powered by an engine having a throttle valve.
In view of the above, various engine brake devices have been hitherto proposed and put into practical use to provide the vehicle powered by the "NTVDE" with a satisfied engine braking, some of which are described in Japanese Utility Model First Provisional Publications No. 63-78142 and 2-96406. These are of a so-called decompression type.
In the device of the '142 publication, an extra exhaust valve is provided in addition to usual exhaust valves, which can open and close the exhaust port of the engine. That is, when, under compression stroke, a corresponding piston moves up near a top dead center, a hydraulic actuator actuates the extra exhaust valve to open to induce engine braking. While, in the device of the '406 publication, given one of paired exhaust valves actuated by a rocker arm is used for carrying out the engine braking. That is, when, under compression stroke, a corresponding piston moves up near a top dead center, a hydraulically actuated stopper arm actuates the given exhaust valve to open to induce engine braking. However, even the above-mentioned engine brake devices have failed to give satisfaction to users due to their complicated and high cost construction.